NAME

       pthread_getattr_default_np,  pthread_setattr_default_np,  -  get  or  set  default thread-
       creation attributes

LIBRARY

       POSIX threads library (libpthread, -lpthread)

SYNOPSIS

       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #include <pthread.h>

       int pthread_getattr_default_np(pthread_attr_t *attr);
       int pthread_setattr_default_np(const pthread_attr_t *attr);

DESCRIPTION

       The pthread_setattr_default_np() function sets the default attributes used for creation of
       a new thread—that is, the attributes that are used when pthread_create(3) is called with a
       second argument that is NULL.   The  default  attributes  are  set  using  the  attributes
       supplied  in *attr, a previously initialized thread attributes object.  Note the following
       details about the supplied attributes object:

       •  The attribute settings in the object must be valid.

       •  The stack address attribute must not be set in the object.

       •  Setting the stack size attribute to zero means leave the default stack size unchanged.

       The  pthread_getattr_default_np()  function  initializes  the  thread  attributes   object
       referred to by attr so that it contains the default attributes used for thread creation.

ERRORS

       EINVAL (pthread_setattr_default_np()) One of the attribute settings in attr is invalid, or
              the stack address attribute is set in attr.

       ENOMEM (pthread_setattr_default_np()) Insufficient memory.

VERSIONS

       These functions are available since glibc 2.18.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌───────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                      │ Attribute     │ Value   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │pthread_getattr_default_np(), pthread_setattr_default_np()     │ Thread safety │ MT-Safe │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       These functions are nonstandard GNU extensions; hence the suffix  "_np"  (nonportable)  in
       their names.

EXAMPLES

       The  program  below uses pthread_getattr_default_np() to fetch the default thread-creation
       attributes and then displays various settings from the returned thread attributes  object.
       When running the program, we see the following output:

           $ ./a.out
           Stack size:          8388608
           Guard size:          4096
           Scheduling policy:   SCHED_OTHER
           Scheduling priority: 0
           Detach state:        JOINABLE
           Inherit scheduler:   INHERIT

   Program source

       #define _GNU_SOURCE
       #include <err.h>
       #include <errno.h>
       #include <pthread.h>
       #include <stdio.h>
       #include <stdlib.h>

       static void
       display_pthread_attr(pthread_attr_t *attr)
       {
           int s;
           size_t stacksize;
           size_t guardsize;
           int policy;
           struct sched_param schedparam;
           int detachstate;
           int inheritsched;

           s = pthread_attr_getstacksize(attr, &stacksize);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_attr_getstacksize");
           printf("Stack size:          %zd\n", stacksize);

           s = pthread_attr_getguardsize(attr, &guardsize);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_attr_getguardsize");
           printf("Guard size:          %zd\n", guardsize);

           s = pthread_attr_getschedpolicy(attr, &policy);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_attr_getschedpolicy");
           printf("Scheduling policy:   %s\n",
                  (policy == SCHED_FIFO) ? "SCHED_FIFO" :
                  (policy == SCHED_RR) ? "SCHED_RR" :
                  (policy == SCHED_OTHER) ? "SCHED_OTHER" : "[unknown]");

           s = pthread_attr_getschedparam(attr, &schedparam);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_attr_getschedparam");
           printf("Scheduling priority: %d\n", schedparam.sched_priority);

           s = pthread_attr_getdetachstate(attr, &detachstate);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_attr_getdetachstate");
           printf("Detach state:        %s\n",
                  (detachstate == PTHREAD_CREATE_DETACHED) ? "DETACHED" :
                  (detachstate == PTHREAD_CREATE_JOINABLE) ? "JOINABLE" :
                  "???");

           s = pthread_attr_getinheritsched(attr, &inheritsched);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_attr_getinheritsched");
           printf("Inherit scheduler:   %s\n",
                  (inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" :
                  (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :
                  "???");
       }

       int
       main(void)
       {
           int s;
           pthread_attr_t attr;

           s = pthread_getattr_default_np(&attr);
           if (s != 0)
               errc(EXIT_FAILURE, s, "pthread_getattr_default_np");

           display_pthread_attr(&attr);

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       pthread_attr_getaffinity_np(3), pthread_attr_getdetachstate(3),
       pthread_attr_getguardsize(3), pthread_attr_getinheritsched(3),
       pthread_attr_getschedparam(3), pthread_attr_getschedpolicy(3), pthread_attr_getscope(3),
       pthread_attr_getstack(3), pthread_attr_getstackaddr(3), pthread_attr_getstacksize(3),
       pthread_attr_init(3), pthread_create(3), pthreads(7)